The present invention relates to apparatus for dispensing biological materials and reagents; and more particularly to apparatus for dispensing individual glassy, porous reagent pills into a laboratory vessel in which a reaction is to take place.
Few biologically active materials are sufficiently stable so that they can be isolated, purified, and then stored in solution at room temperature. As a consequence biological reagents often are provided in dried form to increase their storage stability. In preparing reagents for convenient and efficient testing of biological samples, it is frequently important to obtain dry chemical blends in uniform, discreet amounts. These reagents must be efficiently and economically prepared in small, precisely measured quantities for laboratory use.
One type of carrier which has been used to stabilize doses of biological reagents are glass-forming filler materials, such as a sucrose polymer. A measured amount of a biological reagent solution is incorporated into the filler material, which is a water-soluble or water-absorbing substance. The composite then is freeze dried to produce a sphere shaped reagent pill having a composition which immobilizes and stabilizes the biological reagent. Examples of glass-forming filler materials for stabilizing biological reagents are described in F. Franks, "Long-Term Stabilization of Biologicals", 12 Bio-Technology 253 (1994); U.S. Pat. No. 5,098,893; U.S. Pat. No. 5,200,399 and U.S. Pat. No. 5,240,843.
The biological reagent pills must be kept relatively dry during storage. Otherwise, moisture allows the filler material to change into a rubber state which causes the reagent contained therein to become unstable. As a consequence, reagent pills must be stored in a container that is sealed against moisture.
To use the reagent in a biological procedure or experiment, the carrier pills have to be individually dispensed from the storage container. In order to dispense a single pill at a time, the dispenser has to organize the pills contained in a storage vessel into a stream that is one pill wide. A funnel can be used for this purpose, but spherical the pills tend to jam in the conical bottom thereby blocking the outlet. In addition, dried reagent pills easily become charged with static electricity which causes them to cling to the walls of conventional dispensing apparatus.